The SARS-CoV-2 Total Ab Test Kit (ELISA) is based on immunoenzymatic assay for determination of SARS-CoV-2 antibodies in human serum, plasma (EDTA, Heparin or sodium citrate). The micro plate wells as a solid phase are coated with recombinant SARS-CoV-2 recombinant Receptor Binding Domain protein. In the first incubation step corresponding specific antibodies (SARS-CoV-2-IgG-Ab & some IgM-Ab) present in patient specimens bind to the antigens at the solid phase. At the end of the incubation unbound components are washed out. For the second incubation step SARS-CoV-2 recombinant Receptor Binding Domain protein conjugate (SARS-CoV-2 recombinant Receptor Binding Domain protein peroxidase conjugate) is added which binds specifically to SARS-CoV-2 antibodies (including IgG and IgM) resulting in the formation of typical immunocomplexes. After a second washing step to remove excess conjugate, TMB/Substrate is added (step3). A blue color develops changing to yellow after stopping the reaction with stop solution. The absorbance of calibrators and specimen is determined by using an ELISA micro plate reader. Results for patient samples are obtained by comparison with a cut-off value.